Before Pertussis immunizations were available, nearly all children developed pertussis. In the US, prior to pertussis immunization, between 150,000 and 260,000 cases of pertussis were reported each year, with up to 9,000 pertussis-related deaths.

Pertussis can be a severe illness, resulting in prolonged coughing and vomiting spells that can last for weeks. These spells can make it difficult for a child to ear, drink, and breathe. In infants, it can also cause pneumonia and lead to brain damage, seizures, and mental retardation.

The newer pertussis vaccine (acellular or DtaP) that has been available for use in the US since 1991 is also effective and is associated with fewer mild and moderate adverse reactions when compared with the older (whole-cell DTP) vaccine. In the 1970's, Sweden and Japan's use of pertussis vaccine dropped significantly for various periods of time due to adverse publicity about the older vaccine. These countries experienced a resulting resurgence in pertussis disease.

During the 1970's, widespread concerns about the safety of pertussis immunization led to a rapid fall in immunization levels in the United Kingdom. Within the next several years, a series of pertussis epidemics occurred. More than 100,ooo cases and 36 deaths due to pertussis were reported during a epidemic in the mid-1970's.

In Japan, pertussis vaccination coverage fell from 80% in 1974 to 20% in 1979. An epidemic occurred in 1979, resulting in more than 13,000 cases and 41 deaths.

Pertussis cases occur throughout the world. If we were to discontinue pertussis immunizations in the US, we would experience a massive resurgence of pertussis disease. A very recent study found that in eight countries where immunization coverage was reduced, incidence rates of pertussis surged to 10 to 100 times the rates in countries where vaccination rates were sustained.